Preheat the oven to 350 degrees F (175 degrees C). Scatter the almonds in a jelly roll pan, and toast until golden, about 10 minutes. Set almonds aside, but leave the oven on.
In a food processor, grind the cookies until they are coarse crumbs. Transfer crumbs to a bowl, and stir in the flour. Stir in the 1/2 cup melted butter, and toss to moisten. Butter the bottom of a 10-inch springform pan, leaving the sides unbuttered. Press the mixture onto the bottom of the pan.
Bake until set, about 12 to 15 minutes. Transfer to a rack to cool. When crust has cooled, place it in the freezer for at least 30 minutes.
Butter a 9x13-inch pan; you'll need this for the toffee filling. Set aside 3 cups of the toasted sliced almonds.
In a large saucepan, combine the 1 1/3 cups butter, sugar, water, lemon juice, and salt. Bring to a boil, stirring to dissolve the sugar. Cook uncovered, without stirring, over medium heat until it caramelizes, about 8 minutes. Remove the caramel from the heat, and stir in the vanilla, almond extract, and 3 cups of the almonds. Pour the mixture into the buttered pan, and set aside to cool.
In a microwave-safe bowl, microwave chocolate until melted. Stir occasionally until chocolate is smooth. Spread melted chocolate over the cooled toffee. Immediately sprinkle with about 1 cup of the remaining sliced almonds. Freeze for 1 hour, or until firm. Turn the toffee out onto a work surface, and break it into 1/2 inch pieces.
Let the ice cream soften very slightly in a large bowl. Stir briefly, just until malleable. Fold in the toffee pieces. With a large rubber spatula, spread the ice cream into the crust. Top with the remaining almonds. Place the pie in the freezer. When it has firmed up slightly, cover the top with plastic. Freeze until firm, about 6 hours.
Place the pie in the refrigerator to soften about 20 minutes before serving. Run the tip of a knife around the sides of the pie to loosen. Carefully remove the sides of the springform pan. Cut into wedges with a knife dipped in hot water.